USB device notification

ABSTRACT

A method of notifying clients of a change in a USB including a first client requesting notification of a first change in the USB, detecting the first change in the USB, and notifying the first client requesting notification that the first change in the USB occurred.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to communication in informationprocessing systems and more specifically to notifying parts of systemsthat changes in other parts of the system have occurred.

2. Description of the Related Art

A recent advance in the design of computers involves hot-pluggability,the ability to connect a device to a computer bus while the computer isoperating, and have that device communicate properly with the computer.In the past, computers could only be reliably connected to devices whenpower was not supplied. Now, busses have been designed which functionproperly when devices are connected or powered-up after the bus haspower.

Unfortunately, solving the electrical problems associated withhot-pluggability does not guarantee that the device will communicatewith the computer. The computer must be made aware that the device hasbeen connected, and must be made aware of how that device communicates.This problem is typically solved either by having the computer poll thenewly connected device for this information, or by having the newlyconnected device announce its presence.

Even this does not solve all problems involved with connecting a deviceto a computer after the computer starts operating. Clients, such asapplication programs and other routines may be established on thecomputer, as background processes, foreground processes, or as quiescentroutines awaiting activation. If these clients have already determinedwhich devices are connected before the newly connected device isconnected to the bus, the clients may not be able to take advantage ofthe presence of the newly connected device. Therefore, what is needed isa method or apparatus for notifying clients of the presence of the newlyconnected device. Furthermore, not all application programs or routinesmay want to know of specific devices being connected, so what is alsoneeded is a method or apparatus for selectively notifying clients of thepresence of newly connected devices.

SUMMARY OF THE INVENTION

The present invention, in one embodiment, is a method of notifyingclients of a change in a system including a client requestingnotification of a change in the system, detecting the change in thesystem, and notifying the client requesting notification that the changein the system occurred. The present invention may further includemaintaining a list of requests for notification and removing requestsfor notification when a client terminates a request for notification.

The invention, in an alternate embodiment, is a subsystem for notifyingclients of a change in a system including means for a client to requestnotification of the change in the system, means for detecting the changein the system, and means for notifying the client requestingnotification that the change in the system occurred.

The present invention may be implemented in a system including aprocessor and memory. Likewise, the present invention may be embodied ininstructions encoded in a computer readable medium. Furthermore, thepresent invention may be practiced in a system employing a USB.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the accompanying figures.

FIG. 1 a illustrates a system suitable for use with the presentinvention.

FIG. 1 b illustrates an alternate conception of the system of FIG. 1 a.

FIG. 2 illustrates another system suitable for use with the presentinvention.

FIG. 3 illustrates a process followed in the practice of one embodimentof the present invention.

FIG. 4 illustrates one representation of communication that may occur inpracticing the present invention.

FIG. 5 illustrates an example of a machine-readable medium in accordancewith the present invention.

DETAILED DESCRIPTION

A method and apparatus for USB Device Notification is described. In thefollowing description, for purposes of explanation, numerous specificdetails are set forth in order to provide a thorough understanding ofthe invention. It will be apparent, however, to one skilled in the artthat the invention can be practiced without these specific details. Inother instances, structures and devices are shown in block diagram formin order to avoid obscuring the invention.

Reference in the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the invention. The appearances of the phrase “in one embodiment” invarious places in the specification are not necessarily all referring tothe same embodiment.

FIG. 1 a illustrates a system suitable for use with the presentinvention. The system includes Host 100, HDD (Hard Disk Drive) 110,Keyboard 120, all connected to Bus 130. Additionally, Printer 140 may beconnected to Bus 130, thereby allowing communication between Host 100and Printer 140. FIG. 1 b illustrates an alternate conception of thesystem of FIG. 1 a. Here, the connections are formed with a startopology as typically used when making connections via the UniversalSerial Bus (USB). There is a direct connection between Host 100 andKeyboard 120, between Host 100 and HDD 110, and between Host 100 and Hub135. Printer 140 is optionally connected to Hub 135. In this example,the connections between the devices are the physical connections thatsubstitute for the logical Bus 130. Further information on the USB maybe obtained by consulting the USB Specification 1.0, Jan. 15, 1996,which document is hereby incorporated by reference.

Host 100 may be a computer or other processing apparatus suitable forconnection to peripheral devices. If a computer, Host 100 includes amicroprocessor and may also include some form of internal storage.However, Host 100 may be a controller which serves as a gateway forsignals to and from the devices connected thereto.

FIG. 2 illustrates another system suitable for use with the presentinvention. Microprocessor 210 is coupled to Bus 230, which is coupled toboth Memory 220 and USB Control 240. USB Control 240 is coupled to HDD260, Modem 270 and Printer 280 through USB 250. In a typical USBimplementation, USB Control 240 is a control hub that is directlyconnected to each of HDD 260, Modem 270, and Printer 280. Since the USBallows for hot insertion and removal, Modem 270 may be connected to USBControl 240 after Microprocessor 210 is powered, or Modem 270 may bedisconnected from USB Control 240 while Microprocessor 210 is stillpowered.

Microprocessor 210 communicates with each of the devices coupled to USBControl 240, so Microprocessor 210 must be kept apprised of what isconnected to USB Control 240. Otherwise, Microprocessor 210 may attemptto send instructions to Modem 270 after Modem 270 has been disconnectedfrom USB Control 240. Likewise, Microprocessor 210 may need to accessHDD 260. If HDD 260 was not connected to USB Control 240 whenMicroprocessor 210 initially sought access to HDD 260, Microprocessor210 may fail to complete its processing due to its inability to accessHDD 260.

As mentioned above, Host 100 may be a computer or other processingapparatus suitable for connection to peripheral devices. In oneembodiment, Host 100 includes Microprocessor 210, Memory 220, Bus 230and USB Control 240. Microprocessor 210 may be a processor such as thosemanufactured by Motorola or Intel. Memory 220 may be dynamic randomaccess memory (DRAM), and may also include static RAM or ROM of someform. Note that Memory 220, Microprocessor 210 and Bus 230 may beincorporated on a single device, or each may be composed of severalindividual devices. Typically, Host 100 also includes some form of inputdevice, such as a keyboard, pointing device, or scanner, and some formof output device, such as a display or speaker. Host 100 may also beconnected to input devices such as cameras, storage media, ormicrophones, and may also be connected to output devices such asprinters or storage media. Host 100 may further be connected to suchinput/output devices as modems or touch-sensitive screens, too. Storagemedia (machine-readable media) may include magnetic disks, carrierwaves, optical disks, magnetic tape, memory as described with regard toMemory 220 above, and other forms of media suitable for storage ofinformation.

It will be appreciated that Host 100 may take on other forms, such as anetwork computer or intelligent appliance. Typically, Host 100 will becontrolled by an operating system, such as MacOS available from AppleComputer Corp. of Cupertino, Calif., the Linux operating system, orWindows '95 available from Microsoft Corporation of Redmond, Wash. Undercontrol of such an operating system, Host 100 will execute programs suchas application programs. Likewise, the operating system will includeroutines. These routines and programs will, at times, access peripheraldevices coupled to Host 100. When these routines and programs accessthese peripheral devices, adequate information on which peripheraldevices are currently coupled to Host 100 and what other changes haveoccurred in the system is essential.

These routines and programs may be thought of as clients for purposes ofdiscussion. A method of informing these clients of what changes haveoccurred in the system will now be explained. FIG. 3 illustrates aprocess followed in the practice of one embodiment of the presentinvention, whereby the clients are notified of changes in the system.First, a client requests notification of certain changes in RequestEntry 310. As a result of that request, Parameter Storage 320 occurs,storing parameters of the request submitted by the client. Later, theclient may no longer need information on changes, and therefore willterminate the previous request for notification at Request Termination330. As a result of the termination, Parameter Removal 340 occurs, andthe parameters stored relating to the terminated request are removed.Requests may, in one embodiment, be submitted to a Device Notificationroutine, which will then either store or remove the parameters of therequests as appropriate.

Simultaneous with the operation on requests, the Device Notificationroutine will also determine whether changes are occurring in the system.When a change is detected as in Change Detection 360, the DeviceNotification routine acts upon that change. In Determination 370, theDevice Notification routine will determine which requests haveparameters that include the change detected in Change Detection 360. TheDevice Notification routine will then proceed to Notification 380, thatis notifying each client that submitted a request with parameters thatinclude the detected change. Both cycles Request Entry 310 throughParameter Removal 340 and Change Detection 360 through Notification 380proceed independently of each other.

FIG. 4 illustrates one representation of communication that may occur inpracticing the present invention. Client 410 communicates with DeviceNotification routine 420, such as through requests for notification andtermination of these requests. These requests may, in one embodiment,include an Installed Routine 430, which Device Notification 420 mayactivate in order to notify Client 410 of a detected change. Such anInstalled Routine 430 may communicate with both Client 410 and DeviceNotification routine 420. Device Notification 420 communicates withLower Level 440 to detect changes in the system, and then compares thosechanges with the requests for notification received from Client 410 todetermine whether Client 410 needs notification of the detected changes.Lower Level 440 may be a part of an operating system, implemented ineither hardware, software, or firmware. Alternatively, Lower Level 440may be a physical device such as USB Control 240. Changes in the systemmay include connection or disconnection of a device such as a printer,errors in interfacing or communicating with a device, or a device beingbusy due to previous activity.

In one embodiment, utilized in implementing the present invention inconjunction with the MacOS operating system available from AppleComputer, Corp. of Cupertino, Calif., communication between a Client anda Device Notification routine occurs when the Client calls aUSBInstallDeviceNotification function. Such a function call serves as arequest for notification. A call to such a function looks like: voidUSBInstallDeviceNotification(         USBDeviceNotificationParameterBlock *pb); pb      A pointer tothe USBDeviceNotificationParameterblock

The USBDeviceNotificationParameterblock includes information on whattypes of changes the Client wants notification of and what routine(Installed Routine) to use to communicate with the Client. TheUSBDeviceNotificationParameterblock is defined as: /* DeviceNotification Parameter Block */ structUSBDeviceNotificationParameterBlock ( UInt16 pbLength; UInt16 pbVersion;USBNotificationType usbDeviceNotification UInt8 reserved1; USBDeviceRefusbDeviceRef; UInt16 usbClass; UInt16 usbSubClass; UInt16 usbProtocol;UInt16 usbVendor UInt16 usbProduct OSStatus result; UInt32 token;USBDeviceNotificationCallbackProcPtr callback; UInt32 refcon; };

Field Descriptions <--> usbDeviceNotification The type of notificationThe following notifications are defined: kNotifyAnyEventkNotifyAddDevice kNotifyAddInterface kNotifyRemoveDevicekNotifyRemoveInterface <-- usbDeviceRef The device reference for thetarget device <--> usbClass The class of the target device, usekUSBAnyClass for any class <--> usbSubClass The Subclass of the targetdevice, use kUSBAnySubclass for any subclass <--> usbProtocol Theprotocol of the target device, use kUSBAnyProtocol for any protocol <-->usbVendor The Vendor ID of the target device, use kUSBAnyVendor for anyvendor <--> usbProduct The product ID of the target device, usekUSBAnyProduct for any product <-- result The status of the call <--token The identifier for this notification request --> callback Apointer to the callback routine to be called when the notificationcriteria is satisfiedNote that an arrow ‘-->’ indicates a parameter sent from the Client tothe Device Notification routine, and an arrow ‘<--’ indicates aparameter sent from the Device Notification routine to the Client.A double-ended arrow ‘<-->’ indicates a parameter communicated in bothdirections.Also, note that the parameters sent from the Client to the DeviceNotification routine specify what type of changes the Client seeksnotification of.A first request from a first Client might seek notification of theconnection of any printer.A second request, from either a first Client or a second Client, mayseek notification of connection of any printer manufactured by aparticular vendor, such as Hewlett-Packard.The first request would simply specify a printer as the class of devicein the usbClass field.The second request would specify a printer in the usbClass field, andalso specify the vendor Hewlett-Packard in the usbVendor field.

As will be appreciated, requests for notification may be specific orgeneral, and multiple requests may be made by a single Client, such as aClient seeking access to both a modem and a printer. In one embodiment,the Device Notification routine provides notification by calling acallback routine such as the one supplied in the callback field. Such aroutine would be declared as: typedef void(USBDeviceNotificationCallbackProc)         (USBDeviceNotificationParameterBlockPtr pb); typedefUSBDeviceNotificaitonCallbackProc         *USBDeviceNotificationCallbackProcPtr;

This implementation provides flexibility to the Client, allowing theClient to receive notification of changes in a manner useful to theClient. In particular, the Client may supply a routine as a callbackroutine which alerts it to the presence of a newly connected device, orit may supply a routine that adds a newly connected device to a list ofdevices maintained by the Client. Likewise, notification of removal ordisconnection of a device may result in calling a different routinesupplied in a different request.

Since the Device Notification routine receives multiple requests, itmust maintain a list of each request and its associated parameters. Sucha list would include the parameters passed to the Device Notificationroutine when a client calls USBInstallDeviceNotification and a tokenidentifying each request uniquely. However, if a Client such as anapplication program is terminating, the Client should terminate therequest of notification, and it can do this with a call to aUSBRemoveDeviceNotification function. Such a function is declared as:OSStatus USBRemoveDeviceNotification (UInt32 token); token Notificationidentifier from the previously installed device notification routine.

Upon termination of the request, the information relating to thatrequest that is maintained by the Device Notification routine isdiscarded, and the Device Notification routine no longer seeks to notifythe Client in accordance with that request.

Turning to FIG. 5, an example of a machine-readable medium in accordancewith the present invention is illustrated. In one embodiment,Machine-Readable Medium 500 contains Operating System routines 520embodying Device Notification 420 of FIG. 4, Client 510, the routinesthat embody Client 410 of FIG. 4, List of Requested Notices 530, andCallback routine 540, embodying Installed Routine 430 of FIG. 4. Client510 requests notification of changes in the status of the system.Operating System routines 520, such as those in the MacOS operatingsystem available from Apple Computer, Inc. of Cupertino California,receive the requests for notification from Client 510, manage the Listof Requested Notices 530 which stores the information on each request,detect changes in the status of the system, and call the Callbackroutine 540 when a status change corresponding to a request is detectedor otherwise notify a requestor of the status change. List of RequestedNotices 530 includes information on each request, such as that describedin the above description of the invention as implemented in the MacOSoperating system, and may include a pointer to Callback routine 540 or asimilar callback routine for each individual request. Callback routine540 calls Client 510 or otherwise notifies Client 510 of the change instatus, and may be a portion of Client 510.

It will be appreciated that each of the above routines or portions ofinformation may be stored in machine-readable media (or a single medium)in distributed or whole form. In either case, the information willtypically be stored in a form suitable for execution (such as executableinstructions for example) by a processor such as a microprocessor, orfor use during execution by a processor. Additionally, the information,such as the List of Requested Notices 530, may be changed duringexecution, including creation or deletion of entries or creation ordeletion of the entire List 530. In FIG. 5, the appearance is createdthat everything is stored in integrated or whole form in a singlemachine-readable medium, but it will be appreciated that storage indistributed form in one medium or over multiple media does not departfrom the spirit of the invention.

In the foregoing detailed description, the method and apparatus of thepresent invention has been described with reference to specificexemplary embodiments thereof. It will, however, be evident that variousmodifications and changes may be made thereto without departing from thebroader spirit and scope of the present invention. The presentspecification and figures are accordingly to be regarded as illustrativerather than restrictive.

1. A method of notifying clients of a change in a system comprising: aclient requesting notification of the change in the system; detectingthe change in the system; and notifying the client requestingnotification that the change in the system occurred.
 2. The method ofclaim 1 further comprising: maintaining a list of requests fornotification.
 3. The method of claim 1 further comprising: the clientterminating a request for notification.
 4. The method of claim 2 furthercomprising: the client terminating a request for notification; andremoving a request corresponding to the client from the list of requestsfor notification.
 5. The method of claim 1 wherein: the change in thesystem is connection of a device.
 6. The method of claim 1 wherein: thechange in the system is disconnection of a device.
 7. The method ofclaim 1 wherein: said requesting includes the client supplying acallback routine; and said notifying includes executing the callbackroutine.
 8. A subsystem for notifying clients of a change in a systemcomprising: means for a client to request notification of the change inthe system; means for detecting the change in the system; and means fornotifying the client requesting notification that the change in thesystem occurred.
 9. The subsystem of claim 8 further comprising: meansfor maintaining a list of requests for notification.
 10. The subsystemof claim 9 further comprising: means for the client to terminate arequest for notification; and means for removing a request correspondingto the client from the list of requests for notification.
 11. Thesubsystem of claim 10 further comprising: means for communication to theclient; and wherein: the client supplies the means for communication;and the means for communication is utilized by the means for notifying.12. A machine-readable medium containing a plurality of executableinstructions, which when executed on a processor cause said processor toperform a method of notifying clients of a change in a system, themethod comprising: a client requesting notification of the change in thesystem; detecting the change in the system; and notifying the clientrequesting notification that the change in the system occurred.
 13. Themachine-readable medium of claim 12 wherein the method furthercomprises: maintaining a list of requests for notification.
 14. Themachine-readable medium of claim 13 wherein the method furthercomprises: the client terminating a request for notification; andremoving a request corresponding to the client from the list of requestsfor notification.
 15. The machine-readable medium of claim 14 wherein:said requesting includes the client supplying a callback routine; andsaid notifying includes executing the callback routine.
 16. A systemcomprising: a processor; a memory; a bus, the bus coupled to theprocessor, the bus coupled to the memory; and the processor processing arequest by a client for notification of a change in the system, theprocessor detecting the change in the system, and the processornotifying the client that the change in the system has occurred.
 17. Thesystem of claim 16 wherein: the processor maintains a list of requestsfor notification.
 18. The system of claim 17 wherein: the processorstores the list of requests in memory.
 19. The system of claim 17wherein: the processor processes the client's termination of a requestfor notification by removing a request corresponding to the client fromthe list of requests for notification.
 20. The system of claim 19wherein: the processor receives a callback routine from the client whenthe client requests notification and the processor notifies the clientby executing the callback routine.
 21. A method of notifying clients ofa change in a USB comprising: a first client requesting notification ofa first change in the USB; detecting the first change in the USB; andnotifying the first client requesting notification that the first changein the USB occurred.
 22. The method of claim 21 wherein: the change isconnection of a device to the USB; and further comprising: finding adriver suitable for use with the device.
 23. The method of claim 21wherein: the change is disconnection of a device from the USB; andfurther comprising: deactivating a driver corresponding to the device.24. The method of claim 21 further comprising: a second clientrequesting notification of a second change in the USB; detecting thesecond change in the USB; and notifying the second client requestingnotification that the second change in the USB occurred.
 25. The methodof claim 24 wherein: a change in the USB constitutes a first change andconstitutes a second change.
 26. The method of claim 24 wherein: achange in the USB that constitutes a first change does not constitute asecond change.